A type of laminate designated FR-4 which is produced by laminate molding of a prepreg comprising a glass cloth impregnated with a resin component such as epoxy resin is being widely used as a typical laminate in printed wiring boards for electronic devices. The designation FR-4 is a classification according to standards set forth by the U.S. NEMA (National Electrical Manufacturers Association).
On the other hand, so-called CEM-3 type composite laminates are also known in which glass cloth impregnated with a resin component is laminated as a surface layer on both surfaces of a core layer of nonwoven cloth impregnated with a resin component. For example, Patent Document 1 proposes a composite laminate in which a resin varnish used in a core material contains a filler combining talc and aluminum hydroxide, a compounding ratio between talc and aluminum hydroxide is 0.15:1 to 0.65:1, and the aluminum hydroxide is a boehmite type aluminum hydroxide. In addition, Patent Document 2 describes a composite laminate containing an aluminum hydroxide with a molecular formula of Al2O3.nH2O (where n is a value greater than 2.6 and smaller than 2.9) in an amount of 200 wt % to 275 wt % of resin in an intermediate layer of the laminate.
Patent Document 1: Japanese Patent Application Laid-open No. S62-173245
Patent Document 2: Japanese Translation of PCT Application No. 2001-508002
As electronic devices have become lighter and more compact in recent years, electronic components are being mounted at higher densities on printed wiring boards (circuit boards). Such mounted electronic components may include a plurality of LEDs (light-emitting diodes) and the like that require heat dissipation. Conventional laminates problematically lack adequate heat dissipation properties as substrates for such purposes. Meanwhile, as far as mounting methods are concerned, reflow soldering and, in particular, reflow soldering using lead-free solder which requires a high-temperature reflow process has become the mainstream in the interest of reducing environmental impact. In a reflow soldering process using such lead-free solder, high heat resistance is required in order to suppress blistering and the like. Maintaining drill workability is also necessary. Furthermore, from a safety standpoint, fire retardancy satisfying the V-0 level as defined by the UL-94 standard is required. However, there are no conventional laminates that simultaneously satisfy such thermal conductivity (heat dissipation properties), heat resistance, drill workability, and fire retardancy.